6-Speed Bell housing On SMG

[sapote]

It’s risky to swap another bellhousing as the input shaft bearing can be damaged from wrong clearance.

Find someone to weld the broken pieces back.

[bmwfnatic]

This.

I did this on my own M3 and everything went smooth... but, one thing to note is that you will likely end up with a slight 'whine' from the input shaft bearing, mostly at idle with clutch out. Something to do with the bearing (which resides on the bellhousing side) being perfectly matched to the input shaft (transmission side) at the factory to a very tight tolerance. Using a bellhousing from another unit throws this off just enough and puts some pressure on the bearing, causing a whine. Mine did this for almost a decade and many miles without getting worse or something breaking but it always bothered me to a degree and made me wish I had simply modified the original SMG housing. My car was mostly stock so if yours is modified with extra NVH then you might not care about this.

It’s a 2 part bearing that gets separated, with its inner race staying on the input shaft and the rest of the bearing remaining in the bellhousing. So yes in theory they should stay together.

[PetrolM3]

I have heard of a few people doing this without issue. You will also have to move the manual the detent locking pins from the transmission side and cut threads for the gear recognition sensor.

https://www.mforum.net/forum/e90-m3-sedan-e92-m3-coupe-e93-m3-convertible-2008-2013/diy-ab/84-diy-comprehensive-smg-to-manual-conversion

This.

I did this on my own M3 and everything went smooth... but, one thing to note is that you will likely end up with a slight 'whine' from the input shaft bearing, mostly at idle with clutch out. Something to do with the bearing (which resides on the bellhousing side) being perfectly matched to the input shaft (transmission side) at the factory to a very tight tolerance. Using a bellhousing from another unit throws this off just enough and puts some pressure on the bearing, causing a whine. Mine did this for almost a decade and many miles without getting worse or something breaking but it always bothered me to a degree and made me wish I had simply modified the original SMG housing. My car was mostly stock so if yours is modified with extra NVH then you might not care about this.

[Slideways]

I purchased a six-speed transmission and got scammed. Bought it off of some guy from offerup and didn’t inspect it great. It was dark, so it’s my own fault. Well, get home the next day and notice that the trans mount tab is broken and the part that holds the shifter is cracked. I’m now stuck with a trans that has a good bell housing, but can’t otherwise be used. I’ve searched on the threads here, but couldn’t find anything definitive. Some say it’s straight swap and no issues, while others say it could cause grinding issues due to some slight differences.

Can someone definitively tell me if I can just swap the manual bell housing onto an SMG trans without issue?

I have heard of a few people doing this without issue. You will also have to move the manual detent locking pins from the transmission side and cut threads for the gear recognition sensor.

https://www.mforum.net/forum/e90-m3-sedan-e92-m3-coupe-e93-m3-convertible-2008-2013/diy-ab/84-diy-comprehensive-smg-to-manual-conversion

[Atluisg]

I purchased a six-speed transmission and got scammed. Bought it off of some guy from offerup and didn’t inspect it great. It was dark, so it’s my own fault. Well, get home the next day and notice that the trans mount tab is broken and the part that holds the shifter is cracked. I’m now stuck with a trans that has a good bell housing, but can’t otherwise be used. I’ve searched on the threads here, but couldn’t find anything definitive. Some say it’s straight swap and no issues, while others say it could cause grinding issues due to some slight differences.

Can someone definitively tell me if I can just swap the manual bell housing onto an SMG trans without issue?